Here's a fairly detailed install of how to lower your car with ST Coilovers. Without further adieu, here we go. I'll do my best to remember the size of the bolts and what not, but I might forget... I apologize for crappy pictures. I wasn’t going to get my DSLR filthy.
I suggest using a lift or hoist but it's not required. A second person is also very helpful, but I didn't have one. I assume no responsibility if you get injured or mess up your car. Be careful and take your time.
I started with the rears.
1: Have your car elevated with a lift or on jack stands and remove the trunk liner. Don't cut corners, remove everything. Also pull your wheels awhile.
2: Underneath the car, locate the damper and the lower mount. This is an E12 socket. Remove both bolts.
3: In the trunk, remove the top damper nut. (16mm and 6mm)
4: Back underneath, remove the large bolt and nut (21mm) that holds the brake hub to the suspension arm. You will need a floor jack or screw jack to push up on the spring and release some tension on the bolt. It may fight a little, but it'll come.
5: Release the jack slowly and you can then pull out the spring and damper.
6: Remove the lower damper mount and install it on the new ST damper. (16mm) Put the new covers and bump stops on the damper.
7: Find the new threaded spring perch and coat it with anti-seize. Don't be afraid to get carried away; you can never have enough lube.
8: Back on the car, you'll see a black cup that held the old spring, pry that off with a screw driver or pry bar. The new spring perch with sit in there with the new spring.
9: Pull down the suspension arm and insert the new spring with the perch. You will use the old spring boot on the bottom of the new spring. Make sure everything is lined up and sitting comfortably. There is an orientation of the bottom mount, make sure it's correct.
10: Insert the damper and compress it by hand and send up inside the trunk.
11: Get your jack again and raise the suspension arm up and put the bolt through the brake hub.
12: While you're still under the car put the bolts in the lower damper mount.
13: Back in the trunk replace the top damper mount and bolt.
Do this again on the pass side and rears are done! Oh and replace the trunk liner. Easy, right? I adjusted the perches and about half way down, by the way.
Okay, take a break... Get ready for the fronts. We're going to do the front left.
1: The rears are basic, but the front have sensors. A few, to be exact. ABS, Brake Lining and Headlight Leveling. Remove these all first. You have two behind the strut in and small plastic case. And the leveling sensor has a little arm that looks like a sway bar link. (10mm)
2: Remove the upper part of the sway bar link that mounts the side of the strut. (16mm and 17mm)
3: Remove the outer tie rod end (21mm and T40 Torx) This is removed so we can pull the control arm down to remove the strut.
4: Remove the pinch bolt that holds the strut. (18mm)
5: Lightly hammer a chisel in the cap that pinches the strut. This will help you free the strut easily without too much swearing.
6: Up top, there are three (13mm) bolts that hold the top strut mount. Support the strut because it will drop. You will need an open ended wrench for the bolt underneath the strut tower brace.
8: Now the hub is flopping around. Time to finally use that buddy and a pry bar. My buddy was a 5 foot long pry bar. No picture, but pry the control arm down and swing out the strut assembly. Your chisel should still be in that pinch slot, and the strut should pull out easily.
9: Put the strut assembly in a vise or something secure and compress the spring with two good spring compressors.
10: On top of the strut, there is a 21mm nut, an impact gun works the best and slowly take the nut off. (Warning, this is dangerous. Be careful and make sure the spring is compressed. It will pop.)
11: Here we have the new strut from ST. Again, more lube! Coat the threads with anti-seize.
12: Spin the perch all the way down and put the spring on. You don't need to compress the spring. Install the old top strut mount completely. (22mm and 6mm allen) Make sure the spring is sitting correctly in to the mount.
13: Put the strut into the hub and clamp it down with the pinch bolt.
14: Pry down on the control arm again and put the strut up inside the three mounting holes. Tighten them down nice and snug. From here it's reverse steps, tighten the tie rod, the sensors and the sway bar link. Repeat for the pass side and check out your new ride height. I have 20 threads left available to go lower on the front, to give you an idea of where I have it adjusted.
Hope this helps!
Memorable frustrations include: getting front struts out of and into the car, replacing the trunk liner and adjusting the rears. To adjust the rears without the whole perch spinning, tap a pry bar or screw driver between the perch and the body and use your spanner wrench to turn it. Have fun, take your time and be careful.